nzecp 19 1994 new zealand electrical code of practice for determination of maximum demand

7/27/2019 NZECP 19 1994 New Zealand Electrical Code of Practice for Determination of Maximum Demand

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NZECP 19: 1994 ISSN 0114-0663

COVER PAGE


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NZECP:19 1994

NEW ZEALAND ELECTRICAL CODE OF PRACTICE

for

DETERMINATION OF MAXIMUM DEMAND

in

ELECTRICAL INSTALLATIONS

Issued by the Office of

The Chief Electrical Inspector,

Energy and Resources Division, Ministry of Commerce

Wellington, New Zealand


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THE ELECTRICITY ACT 1992

APPROVAL OF ELECTRICAL CODE OF PRACTICE

FOR

DETERMINATION OF MAXIMUM DEMAND

IN


Pursuant to Section 36 of the Electricity Act 1992 (the Act)

On the 11th day of August 1994 the Secretary of Commerce issued the Electrical Code of

Practice for Determination of Maximum Demand in Electrical Installations (the Code).

On the 25th day of August 1994, pursuant to Section 38 of the Act the Secretary published

in the Gazette a notice of intention to apply to me for approval of the Code, and there has

been consultations with such persons (or their representatives) as will be affected by the

Code and they have had the opportunity to consider possible effects and comment on thoseeffects.

I have considered the comments concerning those effects and where necessary amendments

were made to the Code.

Therefore pursuant to section 38 of the Act, I, Douglas Lorimer Kidd, Minister of Energy,

have this day approved the Code as attached to this approval, which Code shall come into

force on the 1st day of April 1995.

Dated this 4th day of February 1995.

Douglas Lorimer KiddMinister of Energy


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COMMITTEE REPRESENTATION

This Code of Practice was prepared by the Ministry of Commerce, Chief Electrical

Inspectors Office with reference to the following organisations:

Electrical Consultants

Electrical Supply Engineers Association of NZ

New Zealand Electrical Institute

Electrical Contractors Association of NZ Inc

Electrical Engineers

ACKNOWLEDGEMENT

The source material for this Code was derived from Section 2 of Australian Standard

AS 3000-1991.

REVIEW

This Code of Practice will be revised as occasions arise.

Suggestions for improvements of this Code are welcome. Send all comments in

writing to: -

The Chief Electrical Inspectors Office

Ministry of CommercePO Box 1473

WELLINGTON


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CONTENTS

INTRODUCTION ................................................................................................. 3

SECTION 1 ......................................................................................................................... 4

SCOPE AND APPLICATION, REFERENCE DOCUMENTS,

INTERPRETATION, GLOSSARY AND NUMBERING...................................... 4

1.1 SCOPE AND APPLICATION.................................................................. 4

1.2 REFERENCE DOCUMENTS .................................................................. 4

1.3 INTERPRETATION ................................................................................ 4

1.4 GLOSSARY OF ABBREVIATIONS USED IN THIS CODE.................. 6

1.5 NUMBERING SYSTEM OF THIS CODE............................................... 6

SECTION 2

METHOD OF DETERMINING MAXIMUM DEMAND.................................................... 7

2.1 MAINS AND SUBMAINS....................................................................... 7

2.2 FINAL SUBCIRCUITS............................................................................ 7

SECTION 3

DETERMINATION OF MAXIMUM DEMAND IN MAINS AND SUBMAINS ............... 83.1 ASSESSMENT ....................................................................................... 8

3.2 MEASUREMENT ................................................................................... 8

3.3 LIMITATION ......................................................................................... 83.4 CALCULATION...................................................................................... 8

TABLE 1 .............................................................................................................. 10

MAXIMUM DEMAND - SINGLE AND MULTIPLE DOMESTIC

ELECTRICAL INSTALLATIONS.......................................................... 10

FOOTNOTES TO TABLE 1................................................................................. 15

TABLE 2 .............................................................................................................. 16

MAXIMUM DEMAND - NON DOMESTIC ELECTRICALINSTALLATIONS.................................................................................. 16

FOOTNOTES TO TABLE 2................................................................................. 18

SECTION 4

MAXIMUM DEMAND OF FINAL SUBCIRCUITS ......................................................... 19

4.1 GENERAL .............................................................................................. 19

4.2 ASSESSMENT ....................................................................................... 19

4.3 LIMITATION ......................................................................................... 19

4.4 ELECTRIC RANGES, OVENS AND HOBS IN DOMESTICELECTRICAL INSTALLATIONS.......................................................... 20

4.5 CIRCUITS TO WHICH MORE THAN ONE ELECTRICAL

APPLIANCE OR SOCKET-OUTLET IS CONNECTED........................ 20

4.6 INTERLOCKING.................................................................................... 20

APPENDIX A..................................................................................................................... 21

EXAMPLES OF MAXIMUM DEMAND CALCULATIONS.............................. 21


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APPENDIX B..................................................................................................................... 26

B.1 WELDING MACHINES......................................................................... 26


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INTRODUCTION

This Code is intended to assist in the determination of the maximum demands to be

expected in mains, submains and final subcircuits. It also includes the current demands tobe assumed for commonly used electrical appliances, in the determination of maximum

demands in mains, submains and final subcircuits.

The current demand of a final circuit is determined by summing the current demands of all

points of utilisation and electrical appliances in the circuit and, where appropriate, making

an allowance for diversity.

This Code is based on Section 2 of AS 3000-1991 with amendments. It supports the move

for trans-Tasman alignment on electrical safety criteria.


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DETERMINATION OF MAXIMUM DEMAND IN ELECTRICAL

INSTALLATIONS

SECTION 1

SCOPE AND APPLICATION, REFERENCE DOCUMENTS, INTERPRETATION,

GLOSSARY AND NUMBERING

1.1 SCOPE AND APPLICATION

1.1.1 This Code outlines methods for determining the maximum demand in mains,

submains and final subcircuits in electrical installations.

1.1.2 Due recognition has been made of the characteristics of electrical installationswith appropriate diversity.

1.2 REFERENCE DOCUMENTS

The following Standards are referred to in this Code.

AS 1966 Electric Arc Welding Power Sources.

AS 3000 SAA Wiring Rules.

1.3 INTERPRETATION

For the purposes of this Code, the definitions given below shall apply.

1.3.1 Circuit-breaker - means a switch suitable for opening a circuit automatically,

as a result of predetermined conditions, such as those of overcurrent

or under-voltage, or by some form of external control and designed to

interrupt excessive current up to its rupturing capacity.

1.3.2 Connected load - means the rating (in amperes or watts) of the electrical

appliance(s).

1.3.3 Diversity - means a factor that may be applied to the total connected load in

recognition of normal usage and of the fact that all electrical

appliances are not drawing current at the same time.

1.3.4 Final subcircuit - means a circuit originating at a switchboard and to which

electrical appliances are or will be connected.

1.3.5 Fuse - means a composite fitting for opening an electrical circuit by means of

a conductor designed to interrupt the supply of electrical current bymelting when an excessive current flows.


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1.3.6 Mains - means those fittings forming part of an electrical installation that are

used for the supply of electricity to the main switchboard of the

installation.

1.3.7 Maximum demand - means the highest integrated rate of consumption of

electricity over one of the following periods of time:

(a) Instantaneous; or

(b) 15 minutes over any 12 hour period; or

(c) 30 minutes over any 24 hour period.

1.3.8 Point, in relation to fixed wiring, - means the termination of wiring:

(a) At a fitting such as a socket-outlet, a lampholder, a permanent

connection unit, an isolator or a ceiling rose; or

(b) Directly at the terminals of an electrical appliance or aluminaire.

1.3.9 Protective fitting - means a fitting that interrupts the flow of electricity to a

circuit or part of a circuit under conditions of overload, short circuit

or leakage to earth (i.e. a fuse or circuit-breaker).

1.3.10 Socket-outlet - means a fitting that-

(a) Has contacts intended for making a detachable connection with

the contacts of a plug; and

(b) Is, or is to be, fixed or suspended at the termination of fixedwiring.

1.3.11 Submain - means those fittings that-(a) Form part of an electrical installation; and

(b) Are used for the supply of electricity from the main

switchboard to any other switchboard, whether or not through

intermediate switchboards; and

(c) Have their origin at the load terminals of the associated

protective fitting.

1.3.12 Unit - means a flat or a self-contained unit of domestic accommodation that

contains an electrical installation.


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1.4 GLOSSARY OF ABBREVIATIONS USED IN THIS CODE

A Amperes

AS Australian StandardHz Hertz

kVA Kilovolt-amps

kW Kilowatts

m Metres

SOs Socket-outlets

V Volts

W Watts

1.5 NUMBERING SYSTEM OF THIS CODE

1.5.1 Sections are numbered from 1 to 5.

1.5.2 Subsections are numbered by one full stop between two numbers (eg: 1.4).

1.5.3 Clauses are numbered by two full stops between three numbers (eg: 2.1.1).

1.5.4 Subclauses are numbered by three full stops between four numbers (eg:

3.4.1.2).

1.5.5 Paragraphs contain numbering punctuated by one or more full stops together

with a parenthesised letter.

1.5.6 Subparagraphs are represented by lower case roman numerals enclosed in

parenthesis following paragraphs.

1.5.7 Unless otherwise specified, references in this Code to sections, subsections,

clauses, subclauses, paragraphs, subparagraphs, Tables or Appendices are

references to those of this Code.


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SECTION 2

METHOD OF DETERMINING MAXIMUM DEMAND

2.1 MAINS AND SUBMAINS

2.1.1 Subject to subclauses 2.1.2 and 2.1.3, maximum demand in mains and

submains shall be determined by:

(a) Assessment in accordance with subsection 3.1; or

(b) Measurement in accordance with subsection 3.2; or

(c) Limitation in accordance with subsection 3.3; or

(d) Calculation in accordance with subsection 3.4.

2.1.2 Where an electrical installation comprises loads from both domestic and non-domestic electrical appliances, notwithstanding the options available in clause

2.1.1, subject to clause 2.1.4 the maximum demand shall be calculated byadding together the relevant values obtained from Tables 1 and 2.

2.1.3 Where a measured maximum demand in accordance with paragraph (b) of

clause 2.1.1 is found to exceed that obtained by assessment or calculation in

accordance with paragraphs (a) or (d) of that clause, the measured value shall

be the maximum demand.

2.1.4 The maximum demand referred to in subclause 2.1.2 need not be greater thanthe sum of the current settings of the circuit-breakers protecting the final

subcircuits where circuit-breakers are:

(a) Of the fixed non-adjustable type; or(b) Of the adjustable type and have suitable sealing of the operating

current and time settings.

2.2 FINAL SUBCIRCUITS

Maximum demand of final subcircuits shall be determined by:

(a) The sum of the connected load; or(b) Assessment in accordance with subsection 4.2; or

(c) Limitation in accordance with subsection 4.3.


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SECTION 3

DETERMINATION OF MAXIMUM DEMAND IN MAINS AND SUBMAINS

3.1 ASSESSMENT

3.1.1 Assessment for maximum demand in mains and submains shall be the

demand of a similar electrical installation with allowance made for:

(a) Differences because of the size and type of electrical appliances: or

(b) Differences in the size of the electrical installation being assessed; or

(c) The specialised nature of the electrical installation being assessed.

3.1.2 Assessments are advisable where:

(a) The electrical appliance in an electrical installation operates underconditions of fluctuating or intermittent loading, and a definite duty

cycle can be established; or(b) The electrical installation is large and complex.

3.2 MEASUREMENT

Maximum demand measurement of mains and submains shall be determined

by a maximum demand indicator or recorder.

3.3 LIMITATION

3.3.1 The limitation of maximum demand in mains and submains shall be

determined by:(a) The current rating of a fixed non-adjustable protective fitting in the

main or submain; or

(b) The load setting of an adjustable protective fitting, provided the

current and time settings are suitably sealed.

3.4 CALCULATION

3.4.1 For single and multiple domestic electrical installations, calculation of the

overall maximum demand of each phase shall be determined from Table 1 by:

(a) Taking the sum of the values obtained through applying the

appropriate instructions in Columns 2, 3, 4 or 5 of that Table; and(b) Applying them to the appropriate load groups of load groups A to G in

Column 1 of that Table.

Examples of the calculation of maximum demand, using Table 1, for single

and multiple domestic electrical installations, are given in Appendix A.


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3.4.2 For communal services provided for single and multiple units, calculation of

the overall maximum demand of each phase shall be determined from Table 1

by:

(a) Taking the sum of the values obtained through applying theappropriate instructions in Columns 3, 4 or 5 of that Table; and

(b) Applying them to the appropriate load groups of load groups H to M

in Column 1 of that Table.

3.4.3 For non-domestic electrical installations, calculation of the maximum demand

of each phase of the electrical installation shall be determined from Table 2

by:

(a) Taking the sum of values obtained through applying the appropriate

instructions in Columns 2 and 3 of that Table, according to the type of

electrical installation; and(b) Applying them to the appropriate load groups in Column 1 of that

Table.

3.4.4 For the purposes of the calculation, the load connected to each phase

conductor shall be treated separately.


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TABLE 1

MAXIMUM DEMAND - SINGLE AND MULTIPLE DOMESTIC ELECTRICAL INSTALLATIONS

1 2 3 4 5

Complexes of units, a, b

Loading Associated with individual units

Load group Individual domestic electricalInstallation or single unit per phase

2 to 5 units per

phase

6 to 20 units per

phase

21 or more units

per phase

A Lighting(i) Not including lighting that falls

within subparagraph (ii) of thisload group or load group J

below c

3A for 1 to 20 points + 2A for each additional20 points or part thereof

6A 5A + 0.25 A per unit 0.5A per unit

(ii) Outdoor lighting exceeding1,000W in total h, l

75% connected loadNo assessment for the purpose of maximum demand (see load groupH)

B (i) - Socket-outlets not exceeding10A e

- Fixed wired appliances notexceeding 10A and notincluded in other load groups m

15A for 1 to 20 points + 5A for eachadditional 20 points or part thereof

12A + 5A per unit 15A + 3.75A per unit 50A + 2A per unit

(ii) Electrical installationsincluding one or more 15A

socket-outlets (other thansocket-outlets provided tosupply electrical appliances asset out in load groups C, D, E,

F, G and L e, f)

10A 10A 10A 10A


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1 2 3 4 5

Load group Individual domestic electrical

Installation or single unit per phase



2 to 5 units per

phase

6 to 20 units per

phase

21 or more units

per phase

(iii) Electrical installationsincluding one or more 20Asocket-outlets (other thansocket-outlets provided tosupply electrical appliances asset out in load groups C, D, E,F, G and L

e, f)

15A 15A 15A 15A

C Electric ranges, cooking appliances,PCUs, clothes dryers or socket-outletsrated at more than 20A for theirconnection

e

50% connected load 10A + 3A per unit 15A + 2A per unit 15A + 2A per unit

D Fixed wired space heating or airconditioning appliances or saunas

e, g, k

(i) controlled load

Where the full load current is less than the figure obtained under the other appropriate load groups, no assessment forthe purpose of maximum demand. See footnote

k.

(ii) other typesl

75% connected load 75% connected load 75% connected load 75% connected load

E Instantaneous water heatersI

33.3% connected load 5A + 5A per unit 6A per unit 100A + 1A per unit

F Storage water heaters(i ) controlled load

k

Where the full load current is less than the figure obtained under the other appropriate load groups, no assessment forthe purpose of maximum demand. See footnote

k.

(ii) other typesI

Full-load current 6A per unit 6A per unit 100A + 0.8A per unit

G Spa and swimming pool heatersk

Where only one spa or only one swimming pool is present, 75% of that spa or pool.Where more than one spa or more than one swimming pool is present, 75% of the largest spa or pool, plus 25% of each


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1 2 3 4 5




2 to 5 units per

phase

6 to 20 units per

phase

21 or more units

per phase

other spa or pool.Where both spas and swimming pools are present, 75% of the largest spa, plus 75% of the largest swimming pool, plus

25% for each other other spa and swimming pool present.


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1 2 3 4 5

Load group Individual domestic electrical

Installation or single unit per phase

Communal services

LOADING NOT ASSOCIATED WITH INDIVIDUAL UNITS -CONNECTED TO EACH PHASE (PUBLIC LIGHTING,

COMMUNAL LAUNDRY LOADINGS, LIFTS, MOTORS ETC)

H Communal lightingh, l

Not applicable Full connected load Full connected load Full connected load

I Socket-outlets not included in loadgroups J and M below

d, e, f

Fixed wired appliances not exceeding

10A

Not applicable 2A per point 2A per point 1A per point

J Electrical appliances rated at more than10A and socket-outlets for theirconnection.(i) Clothes dryers, water heaters,

self-heating washing machines,wash boilers

e

Not applicable 50% connected load 50% connected load 50% connected load

(ii) Fixed wired space heating airconditioning appliances, saunasg

Not applicable 75% connected load 75% connected load 75% connected load

(iii) Spa and swimming pool heaters Not applicable Where only one spa or only one swimming pool is present, 75% of thatspa or pool.

Where more than one spa or more than one swimming pool is present,

75% of the largest spa or pool, plus 25% of each other spa orpool.

Where both spas and swimming pools are present, 75% of the largestspa, plus 75% of the largest swimming pool, plus 25% for eachother other spa and swimming pool present.


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1 2 3 4 5


Communal services

LOADING NOT ASSOCIATED WITH INDIVIDUAL UNITS -

CONNECTED TO EACH PHASE (PUBLIC LIGHTING,COMMUNAL LAUNDRY LOADINGS, LIFTS, MOTORS ETC)

K Lifts Use Table 2. No assessment for purpose of calculation of maximum demand. UseTable 2 for determination of size of submains.

L Motors Use Table 2, Column 2.Use Table 2 Column 2.

M Electrical appliances such as, potterykilns, welding machines, radiotransmitters, and the like, includingsocket-outlets other than those set outin load groups A to L above.

Connected load to 5A or less. No assessment

for purpose of maximum demand.

Connected load 10A or less:

No assessment for purpose of maximum demand.

Connected load over 5A.By assessment.

Connected load over 10A. By assessment.


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FOOTNOTES TO TABLE 1

(a) For multiphase connections, divide the number of units by number of supply phases, e.g., 16 units on athree-phase supply, 16 3 = 6 units on the heaviest loaded phase (column 4).

(b) Where only a portion of the number of units in a complex of units equipped with fixed wired

appliances, such as electric cooking ranges or space heating appliances, the number of electricalappliances in each category is divided over the number of phases, and the maximum demanddetermined as shown in Example 3 of Appendix A.

(c) Lighting track systems shall be regarded as 2 points per metre of track.

(d) This load group is not applicable to socket-outlets installed in communal areas and connected to the

individual units. Such socket-outlets should be included in load group B.

(e) For the purpose of determining maximum demand, a multiple combination socket-outlet shall beregarded as one point.

(f) Where an electrical installation contains 15A or 20A socket-outlets covered by load group B(ii) orB(iii), the base loading of load group B shall be increased by 10A or 15A respectively. If both 15Aand 20A socket-outlets are installed, the increase shall be 15A.

Where more than two 15 or 20A socket-outlets are fitted the excess are regarded as 10A types for thepurposes of the calculation.

(g) Where an electrical installation includes an air-conditioning system for use in hot weather and aheating system for use in cool weather, only that system which has the greater load shall be taken intoaccount.

(h) Flood lighting, swimming pool lighting, tennis court lighting and the like.

(i) Instantaneous water heaters plus "quick recovery" storage type water heaters having element ratings

greater than 100 watt/litre.

(j) Storage type water heaters, including "quick recovery" heaters not within the scope of footnote (i).

(k) Controlled loading is taken to include only loading to which electricity supply is regularly controlled

by the electricity supplier so that it is available only for a limited period of time each day. Where thefull load current of the controlled load exceeds the maximum demand calculated using all theappropriate items of this Table, the full load current of the controlled load together with the

calculations from load groups A(ii) and H shall be taken as the maximum demand for the electricalinstallation.

(l) In the calculation of the connected load, the following ratings shall be assigned to lighting:

(i) Incandescent lamps. 60W or the actual wattage of the lamp to be installed, whichever is thegreater, except where the design of the luminaire associated with the lampholder permits onlylamps of less than 60W to be inserted in any lampholder, the connected load of that lampholdershall be the wattage of the highest rated lamp which may be accommodated. For multi-lamp

luminaires, the load for each lampholder shall be assessed on this basis.

(ii) Lamps including auxiliary fittings. Full connected load, being the actual current consumed by

the lighting arrangement having regard to auxiliary fittings such as ballasts and capacitors.

(iii) Lighting tracks. 0.5A/metre per phase of track or the actual connected load, whichever is the

greater.


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TABLE 2

MAXIMUM DEMAND - NON DOMESTIC ELECTRICAL INSTALLATIONS

1 2 3

Load group Residential Institutions, hotels, boarding houses,hospitals, accommodation houses, motels

Factories, shops, stores, offices, business premises

A Lighting other than in load group F a, d 75% connected load Full connected load

B (i) Socket-outlets up to 10A other thanthose in load group B(ii)d

5A for first outlet plus 2A for each additional outlet 5A for first outlet plus 3A for each additional outlet

(ii) Socket-outlets up to 10A in buildingsprovided with either separate fixedwired heating and/or cooling appliancesor permanently installed heating and/orcooling appliances powered from otherenergy sourcesb, d

5A for first outlet plus 0.5A for each additional outlet 5A for first outlet plus 0.5A for each additional outlet

(iii) Socket-outlets exceeding 10A d Full current rating of highest rated socket-outlet plus50% of full current rating of remainder

Full current rating of highest rated socket-outlet plus75% of the full current rating to remainder

C Electrical appliances for cooking, heating andcooling, including instantaneous water heaters,

but not electrical appliances included in loadgroups D and J below.

Full load of highest rated appliance plus 50% of fullload of remainder

Full load of highest rated appliance plus 75% of fullload of remainder

D Motors other than in load groups E and Fbelow

Full load of highest rated motor plus 50% of full loadof remainder

Full load of highest rated motor plus 75% of full loadof second motor plus 50% of full load of remainder


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1 2 3

Load group Residential Institutions, hotels, boarding houses,

hospitals, accommodation houses, motels

Factories, shops, stores, offices, business premises

E Lifts (i) Largest lift motor - full-load current(ii) Next largest lift motor - 75% full-load current(iii) Remaining motors - 50% full-load current

For the purpose of this Load Group, the full-load current of a lift motor shall be the current taken from the

electrical supply when moving maximum rated load at maximum rated speed.

F Fuel dispensing units (i) Motors: First motor - full-load currentSecond motor - 50% full-load currentAdditional motors - 25% full-load current

(ii) Lighting - full connected load.

G Swimming pools, spas, saunas, thermal storageheaters including water heaters, space heaters,and similar arrangements c

(i) Continuous elements - full-load current in all cases(ii) Off-peak elements (including off-peak elements which may be connected to the electrical supply at other

than off-peak times by means of a change-over switch or load control systems):66.6% of full-load current where the demand of the rest of the electrical installation as calculated is notless than that of the off-peak element.Full-load current in all other cases.

H Welding machinesIn accordance with Appendix B, taking into account power factor correction.

J X-ray units 50% of the full-load current of the largest X-ray unit, additional units being ignored.

K Other electrical appliances not including thosewithin the load groups above

By assessment.


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FOOTNOTES TO TABLE 2

(a) In the calculation of the connected load, the following ratings shall be assigned to lighting:

(i) Incandescent lamps. 60W or the actual wattage of the lamp to be installed, whichever is thegreater, except where the design of the luminaire associated with the lampholder permits only

lamps of less than 60W to be inserted in any lampholder, the connected load of that lampholdershall be the wattage of the highest rated lamp which may be accommodated. For multi-purposeluminaires, the load for each lampholder shall be assessed on this basis.

(ii) Lamps including auxiliary fittings. Full connected load, being the actual current consumed bythe lighting arrangement having regard to auxiliary fittings such as ballasts and capacitors.

(iii) Lighting tracks. 0.5A/metre per phase of track or the actual connected load, whichever is thegreater.

(b) Load group B(ii) applies to buildings or portions of buildings incorporating fixed wired heating and/orcooling appliances specifically provided to render unnecessary the use of general purpose outlets for

portable electric space heating or cooling appliances. The assessment of whether fixed wiredappliances for heating, cooling, or heating and cooling are necessary to avoid the use of portableelectrical appliances for such purposes, will depend on the location and climate involved.

(c) Controlled loading is taken to include only loading to which supply is available for a limited period oftime each day.

(d) A socket-outlet installed more than 2.3 m above a floor for the connection of an electrical appliancerated at not more than 100W, or for a luminaire, may be included as a lighting point in load group A.


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SECTION 4

MAXIMUM DEMAND OF FINAL SUBCIRCUITS

4.1 GENERAL

4.1.1 Where the methods referred to in clause 4.1.2 are not followed, the maximum

demand of a final subcircuit shall be the full connected load.

4.1.2 The maximum demand of final subcircuits may be determined by any one of

the methods described in subsections 4.2 to 4.6.

4.2 ASSESSMENT

Assessment of the maximum demand of final subcircuits is advisable:

(a) Where the subcircuit has electrical appliances connected that operateunder conditions of fluctuating or intermittent loading, and where a

definite duty cycle can be established; or

(b) Relate to the measured demand of a similar subcircuit with allowance

made for any differences in electrical appliance characteristics.

(c) Where an electrical installation has subcircuits controlled by circuit-

breakers (of the kinds referred to in paragraphs (a) and (b) of clause

2.1.4,) and the assessment of the maximum demand on each subcircuit

is less than the limits set by the circuit-breaker.

4.3 LIMITATION

4.3.1 The limitation of maximum demand of a final subcircuit may be determined

by,-

(a) The current rating of a fixed non-adjustable protective fitting; or

(b) The current rating of an adjustable protective fitting, provided that the

calibration and adjustment is suitably sealed;

(c) The current rating of the electrical appliance or the loading equal to

the full load rating of the terminal fitting for any type of protectivefitting.


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4.4 ELECTRIC RANGES, OVENS AND HOBS IN DOMESTIC


4.4.1 For an electric range, oven, or hob installed in a domestic electricalinstallation, the maximum demand per phase shall be as follows:

(a) For full-load phase rating not exceeding 5 kW ..................... 16A

(b) For full-load phase rating exceeding 5 kW

but not exceeding 8 kW ....................................................... 20A

(c) For full-load phase rating exceeding 8 kW

but not exceeding 10 kW ..................................................... 25A

(d) For full-load phase rating exceeding 10 kW

but not exceeding 13 kW ..................................................... 32A

(e) For full-load phase rating exceeding 13 kW ......................... 40A

4.4.2 An electric oven or hob unit, or a combination of such an oven and a hob unit,

connected to a supply of electricity as a single electrical appliance, may beconsidered as an electric range for the purposes of this subsection.

4.5 CIRCUITS TO WHICH MORE THAN ONE ELECTRICAL

APPLIANCE OR SOCKET-OUTLET IS CONNECTED

4.5.1 A final subcircuit to which more than one electrical appliance or socket-outlet

is connected, shall have a maximum demand that is the lesser or equal to:

(a) The current rating of the protective fitting for the circuit; or(b) The total actual loading of the electrical appliances and socket-outlets

on the circuit.

4.5.2 For the purposes of paragraph (b) of clause 4.5.1, the loading of a socket-

outlet, other than one installed for the connection of a fixed wired appliance,

shall be the full load rating of the socket-outlet.

4.6 INTERLOCKING

Where more than one electrical appliance or motor is supplied from one finalsubcircuit but is interlocked so that only a limited number of such appliances

and motors may be connected at any one time, the maximum demand of the

final subcircuit may be the highest maximum demand obtainable from any

possible combination of such electrical appliances and motors that may beconnected at any one time.


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APPENDIX A

EXAMPLES OF MAXIMUM DEMAND CALCULATIONS

Calculation of maximum demand in single and multiple domestic electrical

installations (Section 3 and Table 1)

Example 1 Determine the maximum demand of a single domestic electrical installation

supplied by single-phase 230V with the following load:

24 light points

10m of lighting track9 single SOs (10A)

8 double SOs (10A)1 x 1 kW strip heater

1 x 50W exhaust fan1 x 10 kW electric range

1 x 2.5 kW control load water heater

Solution: The method of determining demand in accordance with Table 1.

Load Group A24 lighting points, plus

10m of lighting track, plus50W exhaust fan = 45 points

= 3 + 2 + 2 = 7A

Load Group B

9 single SOs, plus

8 double SOs = 17 points

1000W strip heater = 1 point

= 15A

Load Group C

10 kW electric range = 43.48 x 0.5 = 21.7A

Load Group F(i)

Control load water heater 2500W = 11AMaximum demand = 0A (See footnote k to Table 1)

Total Demand

= Sum of load group demands = A + B + C + F(i)

= 7 + 15 + 21.7 + 0

= 44A


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Example 2 Determine the maximum demand of the heaviest loaded phase in a three

phase domestic electrical installation comprising:

26 lighting points (Two Phases)

24 SOs (Two Phases)15A socket-outlet (Single Phase)

16.6 kW electric range (Two Phase)

4 kW air conditioning unit (Single Phase)

12.96 kW instantaneous water heater (Two Phase)

3.6 kW clothes dryer (Single Phase)

and arrange for connection across a three-phase supply as follows:

Red White Blue

13 lights 13 lights15 SOs 9 SOs

15A socket-outlet

10 kW hop elements 6.6 kW oven

4kW air conditioner

6.48 kW instantaneous

water heater

6.48 kW instantaneous

water heater

3.6 kW clothes dryer

Solution: The method of determining the demand in the heaviest loaded phase in

accordance with Column 2 of Table 1 assuming that the electrical installation is balanced as

far as practicable over the three phases, is as follows:

Load

Group

Red

(A)

White

(A)

Blue

(A)

Lighting A(i) 3 3

SOs (10A) B(i) 15 15

15A socket-outlet B(ii) 10

Electric range C 21.8 14.4

Air conditioner D 13.0

Water heater E 9.4 9.4

Clothes dryer C 7.8

TOTAL 41.2 40.4 40.2

Total loading, heaviest loaded phase = Red phase, 41.2A


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Example 3 Determine the maximum demand of the heaviest loaded phase of a three

phase supply to a complex of 80 units comprising the following loads:

Lighting ........................................................................................80 units

SOs (10A) .................................................................................... 80 unitsElectric ranges ...............................................................................17 units

2.5 kW (11A) Fixed wired strip heaters ........................................ 80 units

Quick recovery water heaters ....................................................... 80 units

Loading not associated with the individual units (Communal Services):

House and public area lighting

80 lighting points at 60W each +

20 lighting points at 100W each(Total lighting 6.8 kW)

20 SOs (10A)

10 clothes dryers at 3.6 kW

2 lift motors each 12 kW

5.5 kW three-phase pump motor

4 kW three-phase water supply motor

Solution: The method of determining the demand of the heaviest loaded phase,assuming that the electrical installation is balanced as far as practicable over the threephases, in accordance with Table 1, is as follows:

Number of units per phase, three-phase supply = 80/3 = 27 units over each of two phasesand 26 units on the other phase. The instructions given under column 5 of Table 1 would

therefore be applicable to the electrical installation other than for the electric ranges.

The number of electric ranges per phase = 17/3 = 6 over each of two phases and 5 on the

other phase. The instructions under column 4 of Table 1 would therefore be applicable to

the Load Group C, electric ranges and cooking appliances.


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I ndividual Units

Load

Group

Column

Lighting A(i) 5 27 x 0.5 = 13.5A

SOs (10A) B(i) 5 50 + (27 x 2) = 104A

Electric ranges C 4 6 x 2 + 15 = 27A

Fixed wired strip

heaters

D 5 27 x 11 x 0.75 = 222.75A

Quick recovery waterheaters

E 5 100 + (27 x 0.8) = 121.6A

Total units loading for heaviest loaded phase = 489A

Communal Services

The lighting is taken as being evenly balanced over the phases, i.e:

6,800 = 2,266Wper phase3

(Should the lighting load be arranged for connection to one phase, the loading for Load

Group H would be 6800W).

The 20 SOs are taken as connected as follows: 7 over each of two phases and 6 on the other

phases.

The 10 clothes dryers are taken as connected as follows: 3 over each of two phases and 4 on

the other phase, with loading on heaviest loaded phase = 14 400W.


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Motors:

5.5kW motor = 10.4A per phase (connected load)

4.0kW motor = 8.3A per phase (connected load)

Load

Group

Column

Lighting H 5 2,266 = 9.9A

230

SOs (10A) I 5 7 x 1 = 7.0A

Clothes dryers J(i) 3 0.5 x (14,400) = 31.3A

(230)

Lifts K 5 NIL

Motors L 5 10.4 + (8.3 x 0.5) = 14.6A

Total communal services loading for heaviest loaded phase = 62.8A

Total loading for heaviest loaded phase:

= Units loading + communal services loading

= 489 + 62.8 = 552A


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APPENDIX B

B.1 WELDING MACHINES

B.1.1 For the purpose of Appendix B, the following definitions apply:

B.1.1.1 Duty cycle, in relation to electrical appliances with a fluctuating load

function, such as welders, - means the ratio of the time during which current

flows to the standard period of one minute, expressed as a percentage.

EXAMPLES OF DUTY CYCLE CALCULATI ONS

Example 1:

A spot welder supplied by a 50 Hz system (3,000 cycles/minute) making six 15-cycle weldsper minute would have a duty cycle of:

6 x 15 x 100 % = 3%3,000 1

Example 2:

A seam welder operating 2 cycles "on" and 2 cycles "off" would have a duty cycle of 50percent.

B.1.1.2 Rated primary current - means:

(a) For arc welding machines complying with AS 1966, the marked rated

input current; or

(b) For arc welding machines complying with AS 1966, but where the

machine is fitted with power factor correction fittings, the marked

corrected primary current; or

(c) For all other welding machines, the current obtained by multiplyingthe rated kilovolt amperes (kVA) by 1,000, and dividing by the rated

primary voltage (being the connected loading of the machine).


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B.1.2 ARC WELDING MACHINES

B.1.2.1 The maximum demand of an individual arc welding machine shall be 100%

of the rated primary current.

B.1.2.2 The maximum demand of two or more arc welding machines shall be:

(a) Two largest weldingmachines

100% of each rated primarycurrent; plus (where more

than two)

(b) Next largest welding

machine

85% of the rated primary

current; plus (where morethan three)

(c) Next largest welding

machine


current; plus (where morethan four)

(d) All other welding

machines


current

B.1.3 RESISTANCE WELDING MACHINES

B.1.3.1 The maximum demand for an individual resistance welding machine,-

(a) Where of the type where the duty cycle is unknown, shall be measured

as 70% of the rated primary current for seam and automatically fedmachines, and 50% of the rated primary current for manually

operated, non-automatic machines:

(b) Where of the type where the duty cycle of the welder is known, shall

be measured as the product of a multiplied by b where:

a is the actual primary current, andb is the multiplier given below for the duty cycle:

Duty cycle

(percent)

50 40 30 25 20 15 10 7.5 5 or less

Multiplier 0.71 0.63 0.55 0.50 0.45 0.39 0.32 0.27 0.22

B.1.3.2 The demand for two or more resistance welding machines shall be the sum of:(a) The value obtained in accordance with subclause B.1.3.1 for the

largest welding machine supplied; and(b) 60% of the values obtained in accordance with subclause B.1.3.1 for

all other welding machines supplied.

nzecp 19 1994 new zealand electrical code of practice for determination of maximum demand

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